Polymers and Composites Flashcards

Which processing technique is most commonly used to manufacture continuous fiber thermoset composite aerospace structures?

Answer: Autoclave curing of prepreg layups

Prepreg (pre-impregnated fiber) layups cured in an autoclave under heat and pressure produce the highest quality, void-free thermoset composite structures for aerospace.

Sandwich composite structures use a low-density core between face sheets to maximize:

Answer: Flexural stiffness-to-weight ratio

Sandwich structures place stiff, strong face sheets far from the neutral axis with a lightweight core, enormously increasing bending stiffness with minimal weight addition.

Viscoelastic behavior in polymers means they exhibit properties of both:

Answer: Elastic solids and viscous liquids

Viscoelastic materials combine elastic (energy storage) and viscous (energy dissipation) responses, leading to time-dependent deformation phenomena like creep and stress relaxation.

The purpose of a sizing (surface treatment) on carbon fibers before embedding in a matrix is to:

Answer: Improve fiber-matrix interfacial bonding

Fiber sizing applies a thin chemical coating that improves wettability and chemical bonding between the fiber surface and the matrix, enhancing interfacial shear strength.

Vulcanization of natural rubber involves cross-linking chains with:

Answer: Sulfur bridges

Vulcanization creates sulfur cross-links between rubber polymer chains, transforming it from a weak, tacky material into strong, elastic rubber with reduced creep.

In a woven fabric composite, the 0/90 degree fiber architecture provides:

Answer: Balanced in-plane properties in two principal directions

A 0/90 degree woven fabric provides balanced stiffness and strength in two perpendicular in-plane directions but has lower properties at other angles compared to a quasi-isotropic layup.